When an IPv4/IPv6 (Internet Protocol version 4/6) mobile node hands over to a new network, the IPv4/IPv6 mobile node disconnects an old access network and connects to a new access network to make a communication. A delay in a handover process may result in a non-seamless service in interruption of a real-time service. Such a delay in a handover process also occurs in a Mobile IPv6 (MIPv6). In MIPv6, if a mobile node detects a new access point, layer 2 (L2) handover is performed and layer 3 (L3) handover is then performed, a delay in a handover process is unavoidable.
To reduce the handover delay in MIPv6, IETF (Internet Engineering Task Force) has proposed a fast handover for MIPv6 (FMIPv6). FMIPv6 performs layer 3 handover prior to layer 2 handover, thereby minimizing the handover delay. However, since FMIPv6 requires buffering a data traffic and signaling with a home agent, complexity for a mobile node supporting FMUPv6 increases. Furthermore, in FMIPv6, an access router only supports IPv6. However, since IPv6 and IPv4 networks still coexist, IPv4 also needs to be supported.
To support a handover to provide a seamless service in a heterogeneous network including IPv6 and IPv4 networks, a mobility support system including an IPv6 mobility support server has been proposed. More specifically, an IPv6 mobile node with multiple wireless interfaces establishes L2 protocol through each interface and establishes an active tunnel and a standby tunnel with the mobility support server. In this case, the mobile node makes a communication through the active tunnel and, when moving to another network, activates the standby tunnel to keep performing the communication. In this case, L2 agreement with the new network has been performed and known L3 information is used, thereby reducing the time period for L2 and L3 handover.
However, since each mobile node establishes active and standby tunnels with the mobility support server in the mobility support system, a great amount of load may be imposed on the mobility support server. Accordingly, the mobility support system may not deal in a flexible manner with an increased number of subscriber mobile nodes. More specifically, the increased number of subscriber mobile nodes may cause an increased burden on the mobility support server in terms of establishment and management of tunnels. Furthermore, an immediate increase in the number or capacity of the mobility support servers is limited. In addition, the increased number of subscriber mobile nodes may lead to an increased amount of messages or data to be processed by the mobility support server, resulting in an increased burden imposed on the mobility support server.